AppendChunk and GetChunk Methods Example (VJ++)

This example uses the AppendChunk and GetChunk methods to fill an image field with data from another record.

// BeginAppendChunkJ
import com.ms.wfc.data.*;
import java.io.*;
import com.ms.com.*;
import java.util.*;

public class AppendChunkX
{
   
   // The main entry point for the application.

   public static void main (String[] args)
   {
      AppendChunkX();
      System.exit(0);
   }

   // AppendChunkX function

   static void AppendChunkX()
   {
      // Define ADO Objects.
      Connection cnConn1 = null;
      Recordset rstPubInfo = null;

      //Declarations.
      String strCnn;
      String strPubID;
      String strPRInfo;
      String strMessage = "";
      long lngOffset = 0;
      long lngLogoSize;
      final  int conChunkSize = 100;
      byte[] varChunk = new byte[conChunkSize];
      int intCommand = 0 ;
      int intMulChunkSize,intLastChunkSize;
      Vector varLogo = new Vector();
      BufferedReader in = 
         new BufferedReader(new InputStreamReader(System.in));
      String line = null;
      int noOfRecords;
      int noOfRecordesDisplayed = 5;
      int recordCount = 0;
      String info;
      int indexOfComma ;

      try
      {
         // Open a connection.
         strCnn = "Provider='sqloledb';Data Source='MySqlServer';"
            + "Initial Catalog='Pubs';Integrated Security='SSPI';";
         cnConn1 = new Connection();
         cnConn1.open(strCnn,"","",AdoEnums.CommandType.UNSPECIFIED);

         // Open the pub_info Table.
         rstPubInfo = new Recordset();
         rstPubInfo.setCursorType(AdoEnums.CursorType.KEYSET );
         rstPubInfo.setLockType(AdoEnums.LockType.OPTIMISTIC );

         rstPubInfo.open("pub_info", cnConn1,AdoEnums.CursorType.KEYSET , 
            AdoEnums.LockType.OPTIMISTIC, AdoEnums.CommandType.TABLE );
         System.out.println ("Available logos are : \n");

         noOfRecords = rstPubInfo.getRecordCount();

         // Prompt for the Logo to copy.
         for ( int i = 0; i < noOfRecords; i++)
         {
            recordCount++;
            strMessage = strMessage + 
               rstPubInfo.getField("pub_id").getString() + "\n";
            indexOfComma = 
               rstPubInfo.getField("pr_info").getString().indexOf(",");
            info = 
               rstPubInfo.getField("pr_info").getString().substring(0, 
               indexOfComma );
            strMessage = strMessage + info + "\n\n";
            // Display five records at a time.
            if ( recordCount == noOfRecordesDisplayed)
            {
               System.out.println(strMessage);
               System.out.println("\n\nPress <Enter> to continue..");
               line = in.readLine();
               strMessage = "";
               recordCount = 0;
            }
            rstPubInfo.moveNext();
            // Display last records and exit if last record.
            if(rstPubInfo.getEOF())
            {
               System.out.println(strMessage);
               break;
            }
         }
         System.out.println ("\nEnter the ID of a logo to copy :\n"  );
         strPubID = in.readLine();

         // Copy the logo to a variable in chunks.
         rstPubInfo.setFilter("pub_id = '" + strPubID + "'");
         lngLogoSize = rstPubInfo.getField("logo").getActualSize();
         while (lngOffset < lngLogoSize)
         {
            varChunk = rstPubInfo.getField("logo")
               .getByteChunk(conChunkSize);
            int i = 0;
            while (i < conChunkSize && varLogo.size() < (int)lngLogoSize)
            {
               varLogo.addElement(new Byte(varChunk[i]));
               i++;
            }
            lngOffset =  lngOffset + conChunkSize ;
         }
            //Get the data for New ID from the user.
            System.out.println 
               ("\nEnter a new pub ID [must be > 9899 & < 9999]:");
            strPubID =  in.readLine().trim();

            System.out.println ("\nEnter descriptive text :");
            strPRInfo =  in.readLine().trim();

            //Temporarily add new publisher to publishers table to 
            //avoid getting error foreign key constraint.
            cnConn1.execute("INSERT publishers(pub_id) VALUES('" + 
               strPubID + "')");

            //Add a new record.
            rstPubInfo.addNew();
            rstPubInfo.getField("pub_id").setString(strPubID);
            rstPubInfo.getField("pr_info").setString(strPRInfo);

            //Copy the selected logo to the new logo in chunks.
            lngOffset = 0;

            //Divide logosize in multiples of constant chunk size.
            intMulChunkSize = 
               (varLogo.size()/conChunkSize) * conChunkSize;
            intLastChunkSize = varLogo.size()- intMulChunkSize ;
            byte[] arrChunk  = new byte[conChunkSize];
            byte[] lastChunk = new byte[intLastChunkSize];

            while ( lngOffset < varLogo.size () )
            {
               int ii = 0 ;
               // Copy the logo in constant chunk size.
               if ( (int)lngOffset < intMulChunkSize)
               {
                  while (ii < conChunkSize && 
                     (int)lngOffset < varLogo.size () )
                  {
                     arrChunk[ii] = 
                        ((Byte)varLogo.elementAt
                        ((int)lngOffset)).byteValue();
                     ii++;
                     lngOffset++;
                  }
                  rstPubInfo.getField("logo").appendChunk(arrChunk);
               }
               // Copy the last remaining chunk.
               else
               {
                  while (ii < intLastChunkSize && 
                     (int)lngOffset < varLogo.size () )
                  {
                     lastChunk[ii] = 
                        ((Byte)varLogo.elementAt
                        ((int)lngOffset)).byteValue();
                     ii++;
                     lngOffset++;

                  }
                  rstPubInfo.getField("logo").appendChunk(lastChunk);
               }

            }

            // Update the new recordset with new logo.

            rstPubInfo.update();

            //Show the newly added data.
            System.out.println ("\nNew Record : " + 
               rstPubInfo.getField("pub_id").getString() + "\n");
            System.out.println ("Description : " + 
               rstPubInfo.getField("pr_info").getString() + "\n");
            System.out.println ("Logo Size : " + 
               rstPubInfo.getField("logo").getActualSize() );

            System.out.println ("\n\nPress <Enter> key to continue.");
            in.readLine();

            //Delete new records because this is a demonstration.
            rstPubInfo.requery();
            cnConn1.execute("DELETE FROM pub_info WHERE  pub_id = '" + 
               strPubID + "'");
            cnConn1.execute("DELETE FROM publishers WHERE  pub_id = '" + 
               strPubID + "'");
      }
      catch( AdoException ae )
         {
            // Notify user of any errors that result from ADO.
            
            // Check for null pointer for connection object.
            if(rstPubInfo.getActiveConnection()==null)
                  System.out.println("Exception: " + ae.getMessage());
            // As passing a Recordset, check for null pointer first.
            if (rstPubInfo != null)
            {
               PrintProviderError(rstPubInfo.getActiveConnection());
               PrintADOError(ae);
            }
            else 
            {
               System.out.println("Exception: " + ae.getMessage());
            }
      }
      // System Read requires this catch.
      catch( java.io.IOException je )
      {
         PrintIOError(je);
      }
      finally
      {
         // Cleanup objects before exit.   
         if (rstPubInfo != null)
            if (rstPubInfo.getState() == 1)
               rstPubInfo.close();   
         if (cnConn1 != null)
            if (cnConn1.getState() == 1)
               cnConn1.close();
      }
   }

   // PrintProviderError Function

   static void PrintProviderError( Connection Cnn1 )
   {
      // Print Provider errors from Connection object.
      // ErrItem is an item object in the Connections Errors collection.
      com.ms.wfc.data.Error  ErrItem = null;
      long nCount = 0;
      int  i      = 0;

      nCount = Cnn1.getErrors().getCount();

      // If there are any errors in the collection, print them.
      if( nCount > 0);
      {
         // Collection ranges from 0 to nCount - 1
         for (i = 0; i< nCount; i++)
         {
            ErrItem = Cnn1.getErrors().getItem(i);
            System.out.println("\t Error number: " + ErrItem.getNumber()
               + "\t" + ErrItem.getDescription() );
         }
      }

   }

   // PrintIOError Function
   
   static void PrintIOError( java.io.IOException je)
   {
      System.out.println("Error \n");
      System.out.println("\tSource = " + je.getClass() + "\n");
      System.out.println("\tDescription = " + je.getMessage() + "\n");
   }

   // PrintADOError Function
   
   static void PrintADOError(AdoException ae)
   {
      System.out.println("\t Error Source = " + ae.getSource() + "\n");
      System.out.println("\t Description = " + ae.getMessage() + "\n");
   }
}
// EndAppendChunkJ

See Also

AppendChunk Method | Field Object | GetChunk Method